Known techniques for introducing an impurity into the surface of a solid substrate include a plasma doping method of introducing an impurity into the solid substrate with a low energy after ionizing the impurity (see, for example, Patent Document 1). FIG. 6 shows a schematic configuration of a plasma process apparatus for use in a plasma doping method as a conventional impurity introducing method described in Patent Document 1. In a vacuum chamber 101 shown in FIG. 6, a sample stage 106 is provided for receiving a substrate 109 being a silicon substrate. A gas supplying device 102 is attached to a gas exhaust port 126 of the vacuum chamber 101 for supplying a doping material gas containing an intended element, e.g., B2H6, into the vacuum chamber 101. At an exhaust port 111 of the vacuum chamber 101, a pump 103 is provided for depressurizing the vacuum chamber 101, and it is thereby possible to keep the inside of the vacuum chamber 101 at a predetermined pressure. A quartz plate 122, being a dielectric window of the vacuum chamber 101, is provided with a microwave guide 121 for radiating a microwave into the vacuum chamber 101 through the quartz plate 122. Moreover, an electromagnet 123 is provided so as to surround the vacuum chamber 101. The microwave radiated from the microwave guide 121 and the DC magnetic field formed by the electromagnet 123 interact with each other, thereby forming a magnetic field microwave plasma (electron cyclotron resonance plasma) 124 in the vacuum chamber 101. A high-frequency power supply 110 is connected to the sample stage 106 via a capacitor 125, and it is thereby possible to control the potential of the sample stage 106.
In a plasma process apparatus having such a configuration, the doping material gas introduced in the vacuum chamber 101, e.g., B2H6, is made into a plasma by plasma generation means including the microwave guide 121 and the electromagnet 123, and boron ions in a plasma 124 produced are introduced into the surface of the substrate 109 by the high-frequency power supply 110.
Specifically, the device production includes, for example, forming a thin oxide film on the surface of a silicon substrate (the substrate 109), and then forming a gate electrode on the substrate 109 by a CVD (chemical vapor deposition) apparatus, or the like. Then, using the gate electrode as a mask, an impurity is introduced into the surface of the substrate 109 by a plasma doping method as described above. After forming source/drain regions, for example, by such an introduction of an impurity, a metal wiring layer, and the like, are formed on the substrate 109, thus obtaining a MOS (metal oxide semiconductor) transistor.
Other than those using an electron cyclotron resonance plasma source as described above, known forms of plasma process apparatuses for use in plasma doping include those using a helicon wave plasma source (see, for example, Patent Document 2), those using an inductively-coupled plasma source (see, for example, Patent Document 3), and those using a parallel plate plasma source (see, for example, Patent Document 4).
Patent Document 1: U.S. Pat. No. 4,912,065
Patent Document 2: Japanese Laid-Open Patent Publication No. 2002-170782
Patent Document 3: Japanese Laid-Open Patent Publication No. 2004-47695
Patent Document 4: Japanese National Phase PCT Laid-Open Publication No.
Patent Document 5: Japanese Laid-Open Patent Publication No. 6-61161